With the continuing need for obtaining better performance, fuel economy and polution control of internal combustion engines, systems have been developed which attempt to monitor the condition and the operation of the engine by observing the health and performance of its cylinders. Unfortunately, many of these systems suffer from undesirable drawbacks due to the manner in which they sense and/or analyze the data. For example, some systems attempt to monitor the engine condition by providing a sensor for each engine cylinder, which increases the cost of the system because of the number of sensors employed. Other systems couple the sensors to the engine such that the sensors are exposed to high pressures and temperatures within the cylinders, making the data output unreliable due to sensor failures and also increasing the cost because of the need to replace the damaged sensors. Attempts to avoid sensor failures of this type by installing the sensors in the engine wall have proved difficult to implement.
From a data analysis standpoint, previous approaches do not accommodate the many variables that are introduced into the signal outputs by the placement of the sensors on different cylinders or the different operating modes of the engine. Moreover, conventional approaches lack adequate signal to noise ratios or repeatablility due to the fact that they measure only a small portion of the stress that is generated by the cylinder pressure.